Electric immersion heater assembly



y 26, 1964 L. D. DRUGMAND 3,134,889

ELECTRIC IMMERsION HEATER ASSEMBLY Filed June 22, 1961 21 4 12a 25 Eng 1. I

INVENTOR. I Am LESTER DDRUGMAND A Tram/1s;

United States Patent 3,134,889 ELECTRIC IIVIMERSION HEATER ASSEMBLY Lester D. Drugmand, Pittsburgh, Pa., assignor to Edwin L. Wiegand Company, Pittsburgh, Pa. Filed June 22, 1961, Ser. No. 118,980 Claims. (Cl. 219-526) My invention relates to electric heaters, more particularly to immersion heaters for use in a water tank or similar container, and the principal object of my invention is to provide new and improved heaters of this character.

A further object of my invention is to eifect a cost reduction in the manufacture of immersion heaters without sacrificing any desirable constructional features. Further objects and advantages will appear from the following description.

In the drawing accompanying this specification and forming a part of this application, there is shown, for purposes of illustration, an embodiment which my invention may assume, and in this drawing:

FIGURE 1 is a fragmentary vertical sectional view through a heater illustrating an embodiment of my invention,

FIGURE 2 is an enlarged fragmentary section of a portion of FIGURE 1, illustrating a step in the assembly of the embodiment, and

FIGURE 3is a sectional view corresponding to the line 33 of FIGURE 1.

The disclosed embodiment ofmy invention is adapted generally to be assembled with a container, such as a Water tank T. I

The tank has an opening it) in a side wall 11 and a metallic connection coupling member 12 of customary design is welded to the side wall 11 so that its opening 14 registers with the wall opening 10. The coupling member 12 is usually formed with a square plate section 12a provided with threaded openings 15 in its four corners.

The electric heating element E may be of a cornmercially available form, such as the hairpin type element herein shown, having a bight Eb and a pair of legs E1. As here shown, the heater comprises a metal sheath 16 which may be of copper to resist corrosive action of the contents of the tank. A resistance coil 17 is disposed within the sheath 16 and held in centered relation by means of highly compacted, powdered refractory material 18. Terminal pins 19 are connected to the opposite ends of the coil 17 and such pins extend outwardly of the open end of the legs E1. Suitable means, such as polystyrene bushings 29, are used to close the open ends of the heating element.

A mounting member or plate 21 is preferably square in plan, as shown in FIGURE 3, to correspond to the square section 12a of the coupling member 12. The plate is provided with a pair of openings 22 which may be formed in a stamping operation to provide the usual opening formation consisting of a generally smooth cylindrical portion 23 where the punch enters the plate, and a generally irregular slightly conical portion 23a made as the punch tears the punched slug through the plate. It is to be understood, however, that a smooth, cylindrical hole, such as formed by a drilling operation, may be used in this assembly equally as Well.

The mounting plate 21 is also formed with four bolt holes to pass bolts 25, each bolt having a head 26 adapted to bear against an outer surface 27 of the mounting plate and a threaded shank adapted to be threaded intoa respective hole in the coupling member portion 12a.

A sealing gasket 28, preferably fiat and plate-like, overlies the inner surface 29 of the mounting plate, the gasket being about the same size as the plate and having two openings and four bolt holes coinciding with the openings "ice and holes in the mounting plate. The gasket may be made of any suitable sealing material and preferably is made of a relatively hard gasket material such as, for example, a compressed composition of natural or synthetic rubber and asbestos.

Bushings 30 complete the assembly of the heating element, mounting plate and gasket, each bushing being made of a relatively deformable metal, such as soft copper, and preferably tin plated. Each bushing comprises a head or flange 31 and a cylindrical shank 32. As best seen in FIGURE 2, each bushing fits in the space between a leg E1 of the heating element and the defining surface of a respective set of aligned holes in the mounting plate and gasket. The shank 32 of each bushing may initially be as long as the combined thickness of the mounting plate and gasket and the parts thus far assembled are placed between dies 33, 34 of a suitable press.

The die 33 has a pair of cylindrical portions 35 which fit slidably around the ends of respective heating element legs E1 and have an outside diameter approximately equal to that of the bushing shank 32. The terminal end of each cylindrical portion 35 is shown in FIGURE 2 as ready to press against the end of the bushing shank 32.

The die 34 has a pair of cylindrical recesses 36, each of a diameter to closely receive the head 31 of a bushing. A V-shaped circular ridge or stake 37 is located within each recess and the die has a pair of openings 38 to pass the adjacent portions of the legs E1; the recess 36, ridge 37 and opening 38 being concentric.

As shown in FIGURE 2, the thickness b of the bushing head 31 is slightly greater than the depth a of the die recess 36 so that as the dies are closed upon each other, the bushing head will be urged against the gasket to compress the latter and thus insure a good seal of the connection between the mounting member and the bushing.

The V-shaped stake 37 will enter the bushing head (when the dies are closed on each other) to force bushing material radially inwardly to substantially cold welded relation and good sealing engagement with the adjoining surface of the heating element leg E1. The cylindrical portions 35 of die 33 will enter the respective plate openings 23a and exert sufficient pressure on the end of bushing shanks 32 to deform the latter and cause them to shorten and spread into substantially cold welded relation and good sealing engagement with the surfaces defining the plateopenings 22 and the adjoining surface of the heating element leg E1. Advantage is thus taken of the slightly irregular conical portion 23a of the punched mounting plate opening 22 to firmly lock each bushing in place. This assembly rigidly supports the heating ele-, ment E on the mounting plate 21.

A putty-like filler 20a, such as material sold under the trademark Silastic, is now preferably disposed over the end of each heating element leg E1 and spread so as to fill the cavity produced by the deformation of the bushing shank. A dielectric terminal block 39, of usual construction, is then assembled over the projecting ends of the terminal pins 19, the block having holes 40 to pass such pins. Concentric with the holes 40 are cavities 41 whichreceive, shape and compact the putty-like material so that the latter combines with the polystyrene bushing 20 to prevent entrance of harmful matter to the interior of the heating element.

The terminal block 39 abuts the outer face 27 of 1 the mounting plate 21 and electrical clips 42 are disposed I over the terminal pin ends and the latter are thereafter 'being received in recesses in the terminal block. The

Screws 43 are threaded throughscrews are adapted to firmly hold conductor leads to the clips.

The foregoing comprises the assembly of the electric heater, and to assemble the latter with the tank T, the shanks of the four bolts 25 are passed through the peripheral holes in the mounting plate 21 and gasket 28 and are threaded home in the coupling member holes 15. The coupling member 12 preferably has a gasket surface 44 against which the gasket 28 is compressed to effect a very good seal. It will be noted, from an inspection of FIG- URE 1, that the gasket 28 shields the inner surface 29 of the mounting plate from contact with the contents of the tank and therefore the mounting plate may be made of relatively inexpensive material, such as tin plated cold rolled steel, without any protective cladding as heretofore required.

Since the gasket new forms a unitary part of the heating element assembly, it cannot become lost or misplaced as has frequently happened with the usual loose gasket. Further, the present construction speeds up the assembly of the heater with the tank since no loose gasket need be located on the heater and aligned with the mounting bolts. Also, since the manufacturer may determine the proper gasket for the heater, no assortment of loose gaskets need be stocked by the assembler.

Most water heaters contain a magnesium anode to combat corrosive action of galvanic currents set up during operation of the electric heater and the invention provides the additional advantage that the heating element, prior to its assembly with the mounting plate and gasket, may be tin plated to thus, after assembly and while in operation, minimize the flow of magnesium anode galvanic current in a glass lined tank.- This is of considerable importance since tin plating of the completely assembled heater presents many problems.

The tin plating on the bushings 30, mounting plate 21 and heating element B provides the additional advantage of acting somewhat like a lubricant during pressing operation so that deformation of the bushing is accom-' vantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.

Iclaim:

1. An immersion heater for use with water heater tanks and the like, comprising a metallic mounting plate having an opening therethrough, a plate-like sealing gasket overlying said mounting plate and having an opening coinciding with said plate opening, a metal-sheathed electric heating element having terminal and active heating portions, said terminal portion freely passing through said plate and gasket openings, and a bushing tightly compressed in the space between said terminal portion and the surface defining said mountnig plate opening to rigidly connect said element to said plate, said bushing having a headed portion overlying that part of said gasket surrounding said terminal portion and compressing such part against said mounting plate to seal at the bushing and to hold said sealing gasket assembled with said mounting plate, said mounting plate being adapted to hold said heating element to a wall of said tank with said active heating portion extending through an opening in said tank wall and into said tank for heating the contents thereof, said mounting plate being adapted to compress said gasket against a tank surface surrounding said wall opening to seal against leakage, and said gasket covering and protecting that portion of said mounting plate which otherwise would be subjected to deleterious effects of the container contents.

2. The construction according to claim 1 wherein a plating of relatively soft metal is arranged for disposition between the exterior of said bushing and the plate opening surface and the adjoining part of said terminal portion to provide for intimate sealing inte'rengagement.

3. The construction accordingto claim 1 wherein substantially the entire sheath of said heating element is tin plated prior to its assembly with said mounting plate.

4. An immersion heater for use with Water heater tanks and the like, comprising a metallic mounting plate having a pair of openings. therethrough at its central portion and also having a plurality of bolt holes at its peripheral portion, a plate-like sealing gasket overlying a surface of said plate and covering both the central and peripheral portions thereof, said gasket having a pair of openings and a plurality of bolt holes coinciding with respective openings and holes in said plate, a metal-sheathed hairpin type heating element including a bight and a pair of legs, the terminal portion of said legs passing freely through respective plate and gasket openings, and a bushing tightly compressed in the space between each of said leg terminal portions and the surface defining the respective plate opening to rigidly connect said heating element to said 'plate, each bushing having a headed portion overlying that part of said gasket surrounding the respective leg terminal portion and compressing such part against said mounting plate to seal at the bushing and to hold said gasket assembled with said mounting plate, the bolt holes in said mounting plate being adapted to pass the shanks of headed bolts which are threaded into apertures surrounding an opening in a wall of said tank to hold said heating element to said tank Wall with said legs extending through said wall opening and disposed with said bight within said tank to heat the contents thereof, said mounting plate being adapted to compress said gasket against a tank surface margining said Wall opening to seal against leakage and said gasket covering and protecting that portion of said mounting plate which would otherwise be subjected to deleterious effects of the container contents.

5. An immersion heater for use with water heater tanks and the like, comprising a metallic mounting plate having an opening therethrough, a sealing gasket overlying a surface of said mounting plate and having an opening coinciding with said plate opening, a metal-sheathed electhe heating element having terminal and active heating portions, said element passing through said plate and gasket openings, means connecting and sealing the sheath of said elements to said mountnig plate and sealing the opening in said gasket and fastening said gasket to said mounting plate surface, said mounting plate being adapted to hold said heating element to a Wall of said tank with said active heating portion extending from said mounting plate surface and into said tank and with said terminal portion extending from an opposite surface of said mounting plate, said mounting plate being adapted to compress said gasket against a tank surface surrounding said wall opening to seal against leakage, and said gasket covering and protecting that portion of said mounting vplate surface which otherwise would be subjected to deleterious effects of the container contents.

References Cited in the file of this patent UNITED STATES PATENTS Buehne Nov. 27, 1956 

5. AN IMMERSION HEATER FOR USE WITH WATER HEATER TANKS AND THE LIKE, COMPRISING A METALLIC MOUNTING PLATE HAVING AN OPENING THERETHROUGH, A SEALING GASKET OVERLYING A SURFACE OF SAID MOUNTING PLATE AND HAVING AN OPENING COINCIDING WITH SAID PLATE OPENING, A METAL-SHEATHED ELECTRIC HEATING ELEMENT HAVING TERMINAL AND ACTIVE HEATING PORTIONS, SAID ELEMENT PASSING THROUGH SAID PLATE AND GASKET OPENINGS, MEAN CONNECTING AND SEALING THE SHEATH OF SAID ELEMENTS TO SAID MOUNTING PLATE AND SEALING THE OPENING IN SAID GASKET AND FASTENING SAID GASKET TO SAID MOUNTING PLATE SURFACE, SAID MOUNTING PLATE BEING ADAPTED TO HOLD SAID HEATING ELEMENT TO A WALL OF SAID TANK WITH SAID ACTIVE HEATING PORTION EXTENDING FROM SAID MOUNTING PLATE SURFACE AND INTO SAID TANK AND WITH SAID TERMINAL PORTION EXTENDING FROM AN OPPOSITE SURFACE OF SAID MOUNTING PLATE, SAID MOUNTING PLATE BEING ADAPTED TO COMPRESS SAID GASKET AGAINST A TANK SURFACE SURROUNDING SAID WALL OPENING TO SEAL AGAINST LEAKAGE, AND SAID GASKET COVERING AND PROTECTING THAT PORTION OF SAID MOUNTING PLATE SURFACE WHICH OTHERWISE WOULD BE SUBJECTED TO DELECTERIOUS EFFECTS OF THE CONTAINER CONTENTS. 